Eukaryotic cells have developed a complex machinery that insures the faithful localization of proteins throughout the various intracellular organelles. Improper modulation of intracellular protein traffic underlies a number of inherited human disorders in lysosomal sorting function (I-cell disease) and endocytosis (familial hypercholesterolemia). The Golgi complex plays a fundamental role in regulating veral crucial aspects of intracellular protein and lipid movement. Therefore, an appreciation of protein transit through, and sorting from, the constitutive secretory pathway begs a detailed understanding of how proteins traverse the Golgi stack, and how phospholipids influence these events. Yeast provides an excellent system for the study of Golgi secretory function cause of its tractability to genetic, molecular, biochemical and cell biological analyses. The ultimate goals of the proposed research are to identify and characterize the protein and phospholipid components that drive or otherwise gulate essential Golgi secretory processes in yeast. The power of yeast genetics will be employed to dissect the events by which the - SEC14 gene product effects an essential yeast Golgi function. These studies will include a molecular analysis of genes that encode potential responders to SEC14p function, characterization of the intracellular distribution of their corresponding gene products, and measurements of the phospholipid content of both functional and dysfunctional yeast Golgi membranes. These studies aim to establish a unique experimental foundation for examining how yeast execute essential Golgi secretory functions.